This invention relates generally to friction clutches and more specifically to an improved lever system for clutches of this type.
There is an increasing effort being made toward the use of high speed engines in present-day vehicles. Due to the increased engine speed, it is becoming more of a problem to provide a lever controlled friction type clutch which will operate satisfactorily. Not only do centrifugal forces become a major problem at higher speeds but circumferential forces are also present which must be dealt with in order to insure that the levers will always be in a position to function in their intended manner.
In the past, it has been well known to construct a clutch lever and its associate bearing support means in such a way as to try to counteract these forces. Arrangements providing connections directed to these problems can be found in U.S. Pat. Nos. 3,167,163 and 3,417,884. Both arrangements disclose knife-edge pivotal designs which serve to minimize friction between the engaging surfaces as the lever is pivoted between its operative and inoperative position. If properly controlled, the use of a sharp knife-edge in this type of design is most beneficial since it provides line contact between the cooperating surfaces thereby reducing friction between the parts to a minimum.
The arrangement shown in U.S. Pat. No. 3,167,163 provides locating means for the levers in the form of integral lugs on the pressure plate. These lugs extend in an axial direction and project into openings in the lever. The lever opening and cooperating lug are constructed with a sharp knife-edge and mating right angled corner surface respectively. Pivotal movement of the lever is accomplished by a strut which is located between the lever and cover. When the lever begins to pivot about the strut, a rocking action occurs causing the sharp knife-edge to move away from contact with the corner of the right angled surface. Thus, while the sides of the opening and the right angled surface on the lug provide a satisfactory circumferential and radially outward restraint for the levers they are still susceptible to displacement in a radially inward direction. This occurs due to the fact that, when using a strut to accomplish pivotal movement, the lever opening must be enlarged in a radial direction to accommodate for the rocking action of the strut.
The arrangement shown in U.S. Pat. No. 3,417,844 provides locating means for the levers consisting of a pair of spaced axially extending pins which cooperate with spaced slots provided in the outer sides of the levers. The slots are slightly oversized with respect to the pins in a radial direction to permit tilting action of the levers. Thus, while providing a structure which will positively locate the lever in a circumferential direction the levers can move relative to the pins in a radial direction.
Thus, while designs are known which attempt to counteract both radial and circumferential forces imposed on the levers, none disclose a structure wherein the levers are positively retained with respect to their bearing portions in both a radial and circumferential direction.